JPS58182247A - Formation of projected electrodes of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain micro-pitched projected electrodes by employing a common electrode for plating where a plurality of metal films allowing selective etching are laminated. CONSTITUTION:A solder projected electrode 7 is formed by plating and a resist can be removed in the same way as the conventional method. In this case, however, a plating resist is a little thinner than the conventional one. A common electrode is obtained in the following steps, namely Al, Cr, Cu are sequentially laminated and Al-Cr is formed as the lower layer 4b, while Cu is formed as the upper layer 4a. When the Cu is selectively etched, an interval n between the solder plating 7 and upper layer 4a becomes small since the plating resist is thin. Thereby, the liquid does not transfer smoothly, etching is extremely delayed and the Cu layer 4a is left only at the area under the solder plating 7. Next, the lower layer 4b is etched with the Cu layer 4a used as the mask. Thereafter, the upper layer 4a is etched again and the solder layer is rounded by thermal processing. Accordingly, a solder projected electrode 8 can be completed. With such a structure, a projected electrode 8 can be completed without relation to a diameter of opening of a protection film 3. Moreover, a projected electrode can be micro-pitched in accordance with micro-miniaturization of device and a concentrated depositing stress can also be alleviated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing a common electrode when a protruding electrode is formed on a semiconductor substrate by plating, etc. Conventionally, when a protruding electrode is formed on a semiconductor device, etc., a common electrode layer is formed on the entire surface. However, using a resist, protruding electrodes were formed in the necessary areas by plating or the like, and then the resist and common electrode were removed. If there are multiple common electrode layers, they are removed by etching or the like from the upper layer to the lower layer. There are major restrictions on the shape, and even if devices become more and more finely patterned, it has been difficult to achieve micropitch formation of protruding electrodes such as bonding pads.

The present invention focuses on this point and aims to:
The object of the present invention is to provide a method for forming protruding electrodes that eliminates the above-mentioned drawbacks and allows for micro-pitch formation.Next, the case of forming solder protruding electrodes on a semiconductor device will be explained using drawings as an example.Figs. 1 and 2. , Figure 3 is a sectional view of the main part showing the conventional example.
2 is a silicon substrate, 2 is a bonding electrode formed of Al wiring on the silicon substrate 1, and 3 is a passivation film with a portion above the bonding electrode 2 being open. Reference numeral 4 denotes a common electrode layer made of metal such as Cr, C, L, etc., and is formed on the silicon substrate 1 by evaporation or the like over the entire surface. 07t has the role of passivation M3, ensuring adhesion to the ponding electrode 2, and diffusion between the CtL layer and the At film, which is the ponding electrode 2. The CV film is suitable for forming protruding electrodes. 5 is metsukiresist, 6 is Cu plated several μm under the protruding electrode.
Layer 7 is Pb-8n H/D plated on the CtL layer 6 to a thickness of several tens of μm. After forming the protruding electrodes by this plating, the plating resist 5 is removed and the common electrode layer 4 is removed, as shown in FIG. Next, the solder melted by heat treatment is rolled onto the CW layer 6 to complete the solder protrusion electrode 8. When removing the common electrode 4t by etching or the like, is there any variation in the etching time within the silicon substrate 1, or is the etching done so that no residue remains? If this is done excessively, part of the bonding electrode 2 will be etched, resulting in disconnection.To prevent this, conventionally, the amount of overlap t between the opening of the passivation film 3 and the root of the protruding electrode 8 is set to a sufficient amount. It had to be kept large. t is generally 1
It is about 5 to 25 μm.

For this reason, it is necessary to increase the root diameter of the protruding electrodes 8 by 30 to 50 μm compared to the diameter d of the passivation opening, making it difficult to reduce the spacing between the protruding electrodes 80, that is, to create a micro pitch.

Next, the present invention will be explained in detail with reference to FIGS. 4, 5, and 6.

The steps from forming protruding electrodes by plating to removing the resist are the same as in the conventional method, but the resist is formed slightly thinner. The common electrode layer is made of At% Cr s from the bottom.
Cu, At, -' C, layer is formed as lower layer 4h, C.
Let the tb layer be the upper layer 4α. First, only the Cu layer is selectively etched, but if the metal resist is formed thinly, the solder plated portion 7 of the protruding electrode and the upper layer 14α of the common electrode are etched.
The spacing between the electrodes is small, and the liquid circulation is poor, and the etching is extremely slow compared to other parts.Therefore, as shown in FIG. 4, the Cu layer 4α remains only under the 7 layers of solder plating. Next, C, layer 14α
Using this as a mask, the lower layer 14b of the common electrode, that is, the CR and CT layers, is removed by etching. This is the sectional view shown in FIG. Next, the upper layer 4α is removed by etching again and the solder layer is rounded by heat treatment, resulting in solder protrusion electrodes 8 as shown in FIG.
is completed. In this embodiment, the diameter of the root of the solder protrusion electrode 8 and the diameter of the opening of the tushivation film 3 are almost the same.In other words, the common electrode is divided into an upper layer and a lower layer, selective etching is performed, and the upper layer is etched again. By using this method, it is also possible to make the diameter of the base of the shaft smaller than the diameter of the opening.

As described above, according to the invention, it is possible to form protruding electrodes regardless of the aperture diameter of the tsusivation film, and protruding electrodes, which were previously difficult to form at a pitch of 200 μm or less, are now possible to form devices with a pitch of 100 μm or less. It is possible to make the protruding electrodes micro-pitched in response to the miniaturization of the protruding electrodes.In addition, by reducing the root diameter of the protruding electrodes, the deposition stress or thermal stress concentrated on the protruding electrode forming portion of the silicon substrate is alleviated, which improves the quality of the device. It has great effects such as improving

[Brief explanation of the drawing]

Figures 1, 2, and 3 are cross-sectional views of main parts showing the conventional method for forming protruding electrodes, and Figures 4, 5, and 6 are cross-sectional views of main parts showing the method for forming protruding electrodes of the present invention. It is. 1... Silicon substrate, 291. Ponding electrode, 3... Passivation film, 4... Common electrode, 4α... Upper layer of common electrode, 4b... Lower layer of common electrode, 8... Projection electrode. Figure 1 Figure 4

Claims (1)

[Claims] A common electrode layer for plating is formed of a plurality of metal films that can be selectively etched to maintain adhesion during the formation process of the protruding electrodes that serve as input/output terminals of the semiconductor substrate. A part of the first metal film forming the upper layer is first removed by etching, then a second metal film forming the lower layer is removed by etching using the protruding electrode and the first metal film as a mask, and then the second metal film forming the lower layer is removed by etching. 1. A method for forming a protruding electrode for a semiconductor device, comprising the step of etching away the metal film of step 1.